next-less

Next.js + Less

Import .less files in your Next.js project

Installation

npm install --save @zeit/next-less less

or

yarn add @zeit/next-less less

Usage

The stylesheet is compiled to .next/static/css. Next.js will automatically add the css file to the HTML. In production a chunk hash is added so that styles are updated when a new version of the stylesheet is deployed.

Without CSS modules

Create a next.config.js in your project

// next.config.js
const withLess = require('@zeit/next-less')
module.exports = withLess()

Create a Less file styles.less

@font-size: 50px;
.example {
  font-size: @font-size;
}

Create a page file pages/index.js

import "../styles.less"

export default () => <div className="example">Hello World!</div>

With CSS modules

// next.config.js
const withLess = require('@zeit/next-less')
module.exports = withLess({
  cssModules: true
})

Create a Less file styles.less

@font-size: 50px;
.example {
  font-size: @font-size;
}

Create a page file pages/index.js

import css from "../styles.less"

export default () => <div className={css.example}>Hello World!</div>

With CSS modules and options

You can also pass a list of options to the css-loader by passing an object called cssLoaderOptions.

For instance, to enable locally scoped CSS modules, you can write:

// next.config.js
const withLess = require('@zeit/next-less')
module.exports = withLess({
  cssModules: true,
  cssLoaderOptions: {
    importLoaders: 1,
    localIdentName: "[local]___[hash:base64:5]",
  }
})

Create a CSS file styles.css

.example {
  font-size: 50px;
}

Create a page file pages/index.js that imports your stylesheet and uses the hashed class name from the stylesheet

import css from "../style.css"

const Component = props => {
  return (
    <div className={css.backdrop}>
      ...
    </div>
  )
}

export default Component

Your exported HTML will then reflect locally scoped CSS class names.

For a list of supported options, refer to the webpack css-loader README.

PostCSS plugins

Create a next.config.js in your project

// next.config.js
const withLess = require('@zeit/next-less')
module.exports = withLess()

Create a postcss.config.js

module.exports = {
  plugins: {
    // Illustrational
    'postcss-css-variables': {}
  }
}

Create a CSS file styles.scss the CSS here is using the css-variables postcss plugin.

:root {
  --some-color: red;
}

.example {
  /* red */
  color: var(--some-color);
}

When postcss.config.js is not found postcss-loader will not be added and will not cause overhead.

You can also pass a list of options to the postcss-loader by passing an object called postcssLoaderOptions.

For example, to pass theme env variables to postcss-loader, you can write:

// next.config.js
const withLess = require('@zeit/next-less')
module.exports = withLess({
  postcssLoaderOptions: {
    parser: true,
    config: {
      ctx: {
        theme: JSON.stringify(process.env.REACT_APP_THEME)
      }
    }
  }
})

Configuring Next.js

Optionally you can add your custom Next.js configuration as parameter

// next.config.js
const withLess = require('@zeit/next-less')
module.exports = withLess({
  webpack(config, options) {
    return config
  }
})